1. Field of the Invention
This invention relates to a treatment apparatus for workpieces in which a plurality of treatment stations are provided disposed side by side along the apparatus, and transporter means are provided to transport workpieces from one treatment station to the next along the apparatus. Such treatment apparatus may be used for cleaning, pickling, plating and similar treatments applied to workpieces. Usually, each treatment station will comprise a tank of a liquid into which the workpieces are immersed for treatment but there may be treatment stations where articles are sprayed with a liquid or treated with a gas, for example warm air for drying purposes. The particular details of the process being carried out are not relevant to the present invention.
Many different types of workpiece may need to be treated and the workpieces are commonly supported either on jigs or in open topped baskets or in fully enclosed barrels made of a perforated material to allow access of the treatment medium to the articles. The present invention was devised for a treatment machine in which at least some of the articles to be treated are enclosed in barrels.
2. Description of the Prior Art
It is essential, when workpieces are enclosed in a barrel, to ensure that the treatment medium penetrates fully through the perforated barrel and flows freely around the workpieces. Treatment apparatus has been proposed in which each barrel is provided with an external toothed gear wheel which can engage a drive gear at each of the stations, the individual drive gears being driven by respective electric motors. The barrel is rotated by the motor so that the workpieces inside are tumbled through the treatment medium which percolates into the barrel.
However, this rotation arrangement is of limited applicability since the axis of the barrel needs to be stationary so as to engage the drive gear. The barrel can only be rotated at the treatment station when it is in the treatment medium. Where cup-shaped articles are being treated or the barrel contains a large number of very small articles, quite large quantities of the treatment medium may be lifted out of the tank at the treatment station when the articles are removed from the treatment medium. It would be desirable to be able to rotate the barrel just above the surface of the treatment medium for drainage purposes but this has not been possible with the fixed drive motor and spur-gear arrangement referred to.
There are various different types of treatment apparatus and the invention was devised especially for use with a walking beam type of treatment apparatus, as described in our prior British Pat. No. 1,409,784, for example.
When a walking beam type transporter is used, it has hitherto not proved possible to arrange for rotation of the barrel either in or above the treatment medium.
The type of apparatus referred to as a "walking beam" type of treatment apparatus has a long rigid horizontal beam which can be raised and lowered and also moved longitudinally of the apparatus, for example by means of a suitable arrangement of chains and pulleys with hydraulically or pneumatically operated drive means. The barrels (or jigs or baskets) are suspended from the beam by means of parts which rest on supporting ledges of the beam. This enables the beam to pick up the workpieces, move them longitudinally from one station to another, lower them at the treatment stations into the relevant medium and then disengage from the barrel by slight further downward movement so that the beam can be returned to its original longitudinal position to pick up the next adjacent set of workpieces.
In addition to this movement, the beam can be arranged to perform a reciprocating up and down movement whilst supporting the workpieces at the treatment stations so as to "dunk" the workpieces in the treatment medium to ensure good coverage of the workpieces by the medium. This dunking may be especially useful where the workpieces are provided in an open topped basket. The articles may be packed together and prevent access of the treatment medium but the basket can only satisfactorily be agitated in an up and down "dunking" movement without the risk of losing some of the workpieces.
However, if a walking beam type of machine is to be capable of use to treat articles in barrels as well as in baskets or jigs, it would be desirable to be able to rotate the barrels without interfering with the normal functioning of the machine and in particular to do so independently of the position of the beam so that rotation is independent of dunking and can be carried out whether the barrel is immersed at, or disposed above the treatment station.